Bijou's use for Cuisenaire rods

A lovely friend let a borrow a really beautiful set of Cuisenaire rods.  They were a huge hit right away.  Zion has already mastered some simple addition with them all on her own.  Bijou has used them to do some math, but this is really what she prefers to do with them.

Here's a little known fact about Bijou.  I know that I have mentioned in the past that she is quite the cantankerous little girl.  Well, if you REALLY want to send her into fist and hysterics, let her build something (with blocks or dominoes or, in this case, Cuisenaire rods) and it fall down.  It will completely ruin her day.  So this is pretty impressive for her.  These rods are NOT easy to build with (without them falling).  She was very proud of herself.